One stupid question...
 

Could be possible that in the next WinUAE would have three different settings for filters? They are: Native, Native (VGA) and RTG. Thats because I would like to have a special filter for Multisync and other screen modes that are using the VGA ability of the AGA chipset.

Or then rename the RTG settings simply as "VGA", and make it operate on both native chipset VGA and RTG...

And now, is it possible? Hmm? Hein? ;)

"VGA" mode is not that simple.. For example some programmed modes are PAL/NTSC monitor compatible. Technically it is mode that has ~>30KHz line rate but I don't think that can work perfectly either..